hdu 3650 Hot Expo（TwoPointer）

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

int a[1000000];

int main(){
    int n;
    while(scanf("%d",&n),n){
        memset(a,0,sizeof(a));
        int x,y;
        for(int i = 0; i < n; i++){
            scanf("%d%d",&x,&y);
            a[x]++;
            a[y+1]--;
        }
        int ans = 0,sum = 0;
        for(int i = 0; i < 86405; i++){
            sum += a[i];
            ans = max(ans,sum);
        }
        printf("%d\n",ans);
    }
    return 0;
}